DE2050903C3 - Process for the separation and recycling of the unreacted starting materials in a urea synthesis from ammonia and carbon dioxide - Google Patents

Description

3 4

essentially CCX-free urea solution top example

side into the second decomposer 13 and meets in the - _. . . .

Countercurrent to the inert gas, which is located at the bottom of the In line 6 of the drawings

Detergent 13 was introduced via line 16. Reaction mixture of the following composition

In the following stripping process, the solution becomes 5 40 q _U / ₀

all ammonia freed; in this way, 140% of _{the NK 1}

Bottom of the decomposer 13 is an aqueous, essentially CO ₂ 29 * 0%

borrowed pure urea solution and deducted after- CO (NH ₂ ) ;. 170%

following treatment processes via the line H ₂ O ·: - °

14 supplied. The mixture from the head of the zer- io 100.0 ⁰ zo

setzers 13 coming gases and vapors, that.

Essentially consisting of NH ₃ , inert gas and water vapor. After the mixture has passed through the decomposer 8

is formed, is condensed via line 15 - the following compositions result; n

sator 17 passed; the condensed part is via the line 12:

Line 23 put into line 11 and then in the 15th 27 0 ° /

Circuit returned to the synthesis zone that does not contain NH ₂ 20 »/

condensable gases are via line 18. CO., · Anno /

to the washing tower 19 and meet in the counter- CO (NH ₂ ) ₂ Tf '"' ^e

current to the ^ O : - 'introduced by line 24

Washing liquid. _ao 100.0%

From the bottom of the washing tower 19, an ammonia solution emerges through line 22; from the head The liquid of the above together the cleaned inert gas escapes, which is passed through the decomposer 13 for 20 to 20, and out led to the compressor 21 and via 16 to the bottom of the line 14 is a mixture of the following additives Decomposer 13 for stripping returned as the composition of: will.

A large number of possible embodiments NH ₃ 0.5 »/ 0

for this schematic arrangement are self- CO, "' ⁵ J

understandable for the device for purifying CO (NH ₂ J ₂ 'S · "'

Inert gas, which is caused in the decomposer 13 to 30 H ₂ O ■ ^zz '° ^{/ o}

circulate, possible; but of course also 100.0% for the working pressure of the various devices

such as B. the synthesis device 5, the carbamate Obviously, an excellent cleaning

decompose 8 and 13, the carbamate capacitor 10. _{achieve gU} ng by such a process; one

An important modification of the scheme after 35 excellent purification obviously means one

F i g. 1 results from the fact that for the decomposer 13 the recovery of the product, which is marked as a waste, is

grazing means a weight from an external source has been converted.

Inert gas, which has been worked for the above-mentioned work, is fed back in a synthesis pressure from an external source in the circuit 150 kg / cm ² . In the first stage, ammonia was used as a can after it was a possible cleaning agent. The temperature was subjected to the soldering treatment. For example, solution at the outlet of the first stripper can be _{supplied to this N 2} + 3 H _g , which from a 190 ° C; the amount of ammonia used in the device for the preparation of a mixture for the 200 kg / t of urea formed. The second Ab ammonia synthesis is coming. Streifer was operated with nitrogen, which

In this case - the amount of inert gas applied to FIG. 45 is 200 kg / t formed Bezvig - the lines Ifi and 16 are expediently urea, and the temperature of the solution is connected to such a device, aisle from the second scraper at 190 ⁰ C.

Indeed, it is desirable that close to the am-

Apparatus for urea production such a quantity of monium carbamate was 2300 kg / t formed

for ammonia synthesis is available. 50 urea; the solution obtained contained practically

The following example illustrates the invention. Where no biuret and only 0.5 percent by weight ammonia

Unless otherwise stated, the and 0.5 percent by weight of carbon dioxide are as in FIG

Numbers by weight percent. Table given.

1 sheet of drawings

Claims (1)

condenses, in which water vapor at high thermal Claim: mixed level is generated. Because this water reuse steam in other parts of the system. Process for separation and recycling can be det, the efficiency is increased, the unreacted starting materials at 5 The phase coming from the condenser is returned to the synthesis zone in the circuit at 150 to 300 ° C and 50 to 300 atmospheres.
carried out urea synthesis from ammonia The liquid, exiting at the bottom of the decomposer, and carbon dioxide through thermal decomposition, practically CO _a -free phase, is added to a second phase of the synthesis effluent in a first stage, further decomposer, in which an inert gas (N. ,, N ₂ tere decomposition of the io and H _{2 obtained in the first step} and / or other) as a stripping means of liquid effluent in a second stage and det is. Stripping off the unreacted starting materials The second decomposer is also heated and with: the help of an inert gas, thus essentially working at synthesis pressure,
draws that all decomposition The gaseous, _{saturated with NH 3} and H * O, from stubborn under practically the same inert current coming from the syn- thon to the second decomposer thesedruck given pressure conditions to a condenser, in which heat is returned and in the first stage with the help of is obtained, with water vapor on high ther-ammonia strips off. mixed level is generated. The part that condenses siert, is returned to the synthesis zone in the circuit, while the inert, possibly not condensed part of a washing process for re- win the still contained NH _{3 is} supplied. The inert gas emerges from such a washing process practically pure and, after it is compressed again 25 is a second decomposition, as before mentioned, recycled. From the German patent specification 1 157 212 it is from the bottom of the second decomposer a known, the unreacted starting materials from an aqueous solution of practically pure urea, at 150 to 300 ° C and 50 to 300 atmospheres, which is exposed to further treatments,
Urea synthesis carried out from ammonia 30 revealed the advantage of being able to work further decomposition in each part of the and carbon dioxide by thermal decomposition of the device at a pressure equal to the synthesis-synthesis effluent in a first stage. Except when the liquid vapors to be condensed obtained in the first stage are set at high pressure, which makes it possible to generate water vapor in a second stage and stripping the borrowed, which can be used in various raw materials with the help of one of the parts of the system can separate and recycle inert gas. this results in a considerable simplification of the In such a process, the biuret drive regulation and the number of necessary education is practically impossible to avoid completely. Devices if different pressure values are According to the invention, this disadvantage will now be addressed, is reduced,
40 Since, in addition, recompressions are not known, all decomposition stages are under agile, the energy consumption is low, which practically the same as the synthesis pressure carries out in this part of the device on the necessary speaking pressure conditions and in values for the circulation of the inert gas stream in the first stage with the help of ammonia. is adorned. Surprisingly, it has been shown that an aqueous solution of highly pure urine is obtained in the first decomposer with a stripping with substance in the first decomposer which is made only 0.5% ammonia, 0.5% with the help of ammonia.
Contains carbon dioxide and no biuret. The drawing shows the scheme of the already briefly mentioned of all processes mentioned in the effluents from the synthesis,
The device contains compounds (carbamate, NH ₃ and CO _{2 via lines 1 and 2} Carbonates NH ₃ ) by an arrangement which is introduced into the synthesis device 5. The synthesis pressure works syntically, thus results in theses products which essentially consist of urea, practically pure aqueous urea solution. Carbamate, NH ₃ , CO ₂ and water are made up The grain from the urea synthesis device 53 is conducted via line 6 to the first decomposer in the countermove mixture of urea, carbamate, ammunition with ammonia. This ammonia is monia, carbon dioxide and water is drawn from line 1 through line 3, given ver-carbamate decomposer, which essentially vaporizes and overheats in heat exchanger 4 and works at synthesis pressure. In countercurrent to the ge fed into the decomposer 8 via the line 7,
60 In the decomposer 9, the carbamate decomposition takes place on form igen ammonia, which is the reason for the heating and the wiping effect of the wiping agent mentioned, the overall production of the ammonia. Carbamates favors. From the head of the decomposer over the line The carbamate decomposer itself is heated, so that 9 incoming vapors are converted into condensate to promote decomposition. £ 5 sent to tor 10, in which water vapor is generated The gaseous one wifd at the top of the carbamate decomposer; the condensed phase is circulated through drawn stream, which essentially consists of NH ₃ , CO _2, the line 11 recycled to the synthesis zone. and H _a O exists, a condenser con- From the decomposer 8 passes over the Leituni »12 Hv